Automatic diaphragm working by means of a photoelectric cell, a light-sensitive element, or the like



2,163,737 TRIO June 27, 1939.

F. B. A. PRINSEN AUTOMATIC DIAPHRAGM WORKING BY MEANS OF A PHOTOELEC CELL. A LIGHT-SENSITIVE ELEMENT, OR THE LIKE Filed Sept. :50, 193:5

% B, Prim s/2 Patented UNITED STATES PATENT OFFICE alum-i AUTOMATIC DIAPHRAGM WORKING BY MEANS Li PHOTOELECTRIC CELL,

I'I'IVE ELEMENT LIGHT-SENS LIKE A ,ORTHE Frederik Bertha: Archibald Prinsen,

Sellminlen; Netherlands Application September 30, 1933, Serial No. 891,721

In the Netherlands October 4, 1932 a Claim. (0i. 95-64) electric cell, a light sensitive element (Spermschichtzelle) or the like.

Devices have already been proposed whereby photoelectric cells are used for adjusting the diaphragm. Hereby, however, an amplifier is used, supplying the current which is large enough to move an iris-diaphragm, by means of a motor or any other dynamical system, over tooth wheels or levers. The saidsystems need at the same time a source of. current which has to supply the electric energy for the amplifier and the motor. It is obvious that the said'systems are not adapted to be applied to amateur cameras. At most they may be applied to studios with stationary cameras.

The invention meets the said drawbacks by this thai'if the diaphragm is constructed so that the current supplied by a photoelectric cell or the like already sumces for obtaining the desired adjusting.

In the accompanying drawing:

' Figures 1 and 2 are front elevations of two forms of automatiodiaphragms constructed in accordance with the invention, and

Figure 3 is a section of Fig. 1.

Referring to the drawing in detail, the diaphragm consists of. a tapering cleft made in a shutter I. This shutter is mounted'on a balanced and movable dynamic system constituted, for

instance, by a magnet 2 and a coil 3 pivoted on trunnions. Very light materials are used, whereby it is possible to compose a device which is so very sensitive that a current of a iew micro-- 'amperes is suiiicient for adjusting. The system can be returntlinto its position of rest by very thin'spiral springs. I

By this, construction the current, which is directly supplied when a photoelectric cell 6 or the like is exposed to light, suiflces for obtainingv the desired adjustment pi the diaphragm through its connections 6a with-the coil}, even in case of a very small light sensitive element of a diameter of 13 mm. which is screened so that only the light reflected bythe object to be photographed will strike the cell.

The system can befbuilt so that the magnet 2 of the dynamical system encloses the objective.

A considerable advantage is eiiectedv by a device wherein two slitted diaphragms working in ways kept more in the centre, as shown in Fig. 2.

The dynamic systemsmay be arranged oppositely in one and the same magnet.

The light sensitive element may be ring-shaped so that it can be mounted also around the ob- 6 jective.

By arranging filters or a light-shutter, which may be closed to a greater or less extent, in front of the photoelectric cell or light-sensltive-element 6 the diaphragm. adjustment may be adapted to 1 0 various sorts of photographic material.

, The said diaphragm-adjustment may also be adapted by arranging switchable resistances in a the circuit or by field variations in the magnet.

Instead of a slitted diaphragm equivalent other 15 v diaphragms, e. g., grid-diaphragms may also be nected to the moving coil of the dynamical system.

Fig. 2 represents an objective provided with two slitted diaphragms la working in opposite direction, the dynamical systems are arranged 30 in thesame magnet which in this case is composed of two parts 2a.

Fig. 3 represents the cross-section of an ob jective l withdynamical system 3 and slitted diaphragm 4 whereas an annular light-sensitive element 6 provided with a screening-device 5 for the direct light is also arranged. f

I claim:

1'; In a photographic camera, a photographic object lens, a device for the control of light en- 'tering the camera through said object lens, a

photoelectric cell, a moving coil instrument deriving current from the photoelectric cell, means whereby the said device is controlled by the moving coil instrument, and a magnet tor the production of a magnetic field for the moving coilinstrument,'the said photo-cell surrounding the optical axis of thephotographic object lens, said light control device including at least one pivoted diaphragm element having a substantially hyperbolic curved slit tapering in the direction of movement of said element.

2. In an automatic diaphragm for photographic cameras, a diaphragm element, means mounting said element for pivotal movement, means into; a photoelectric cell for controlling the movement of said diaphragm element, said diaphragm element forming the dlsplaceable por-' tion of a rotary coil meter of the d'Arsonval type energized by the photocell-current, said diaphragm element having a slit of substantially hyperbolic form.

3. In an automatic diaphragm for photographic cameras, a diaphragm element, means mounting 10 said element for pivotal movement, means ineluding a photoelectric cell for controlling the movement of said diaphragm element, said diaphragm element forming the displaceable por- 

